Treatment of fiber and the product



Patented Aug. 6, 1935 PATENT OFFICE TREATMENT OF FIBER AND THE PRODUCTBruno E. Roetheli, Boston, Mass.

No Drawing. Application July 2, 1932, Serial No. 620,735

11 Claims.

products of this nature, and to produce an improved natural and/orartificial silk product.

The invention provides on the fiber or fabric insoluble compounds oflead in commercially useful amounts, whereby the weight thereof isincreased and a variable delustering effect is attained to the extentdesired by the operator.

Various proposals have been made for the weighting of silk fibers,principally by the use of tin compounds. It has heretofore been believedto be impossible to accomplish any considerable weighting with leadcompounds without a preliminary treatment of the materials by theapplication of tin or other metal salts, or other preliminary treatmentto create in the fibers a special affinity for lead. In U. S. Patent No.1,579,628 to Berg, et al., for example, it has been suggested to subjectsilk fibers to substantial weighting with tin to create in the fiber anaffinity for lead, and then to treat the fiber with a soluble leadcompound. Preliminary treatment with tin, has, however, a highlydeteriorating effect on silk and rayon, decreasing both the tensilestrength and the elasticity of fibers processed in this manner. Thepresent invention provides an improved and practical method for theWeighting and delustering of natural and artificial silks directly witha lead compound. The necessity for any preliminary treatment of thefibers is dispensedwith, and the deteriorating effect on the fiber ofsuch preliminary treatment is avoided. The process results in a muchimproved weighting operation and in 'a decidedly superior product.

I have discovered that lead in substantial amounts is readily acceptedby .natural and/or artificial silk fibers, without the necessity for anypreparatory treatment to create in the fiber a special affinity forlead, if the'lead is applied in the form of a basic solution of a leadcompound. I have found the basicity of the lead solution with which thefiber is treated to be the only agency necessary to cause the fiber totake up substantial amounts of lead and to create the desiredaffinitybetween thefiber and the lead. Ihave further found that byvarying the basicity the degree of delustering of artificial silk may becontrolled. The basic lead compound itself may be dissolved in asuitable solvent, or neutral or slightly acid lead compounds may bedissolved and the solution then made basic to the extent desired inaccordance with principles hereinafter set forth. The solvent employedfor the lead compound must be one, such as water, which does not affectthe fiber deleteriously. As examples of suitable lead compounds may bementioned the water-soluble acetate and the nitrate, the acetate beingpreferable because of its greater solubility in water.

The desired basic lead solution may be obtained by the action of-alkalis such as ammonia, sodium hydroxide or potassium hydroxide on asolution of neutral or slightly acidic acetate of lead. or by dissolvingoxides of lead in a solution of neutral or slightly acidic acetate oflead, the latter method being preferable. In the use of strong basessuch as sodium hydroxide. or potassium hydroxide, care should obviouslybe taken to use concentrations of alkali which, with the lead compound,will furnish the maximum amount of lead in basic solution. As theprinciple of operation of my invention requires the presence in solutionof lead ions and a sufficient quantity of hydroxyl ions to impart abasic reaction to the solution, it is obvious that only those basesand/or concentrations thereof which provide those ions in solutionshould be used and bases and/or concentrations thereof which causeprecipitation of 'either or both of those ions are undesirable to theextent that such precipitation occurs.

The most favorable degree of basicity for the practice of my inventionvaries somewhat according to the nature of the fiber to be treated. Thisapplies especially to artificial silk fibers, depending upon the processby which they have been manufactured. Thus artificial silk produced bythe viscose process, the nitrocellulose process, the cupro-ammoniu'mprocess or ester types such as cellulose acetate, require each asomewhat different degree of basicity for best results. The preferredbasicity in any particular case is readily determined in practice.

Generally speaking, the higher the basicity used,

the more the natural lustre of the fiber or fabric is reduced. Thedelustering effect of the more basic solutions is especially useful inthe processing of artificial silk goods, in which case the undesirableglossy appearance of the fiber or fabrics is eliminated, either in partor entirely,

according to the basicity of the lead solution used. As an example ofthe practice of my process, I may proceed as follows:

The fibers or fabrics to be weighted, or weighted and delustered, areimmersed in a basic solution of a lead salt, preferably a basic solutionof lead acetate, the basicity of which varies according to the type offiber treated. I have obtained excellent results with a pH of eight orslightly higher. The solution may be either cold or warm, and the timeof immersion for best results is about 30 minutes. The excess ofsolution is then removed in the .usual manner, by centrifugal machinesor otherwise, and the fibers or fabrics are rinsed thoroughly in coldwater. The wash waters may be collected for the purpose of recoveringthe lead lost in the washing operations.

After washing, the fibers or fabrics are treated in a so-called fixingbath, the purpose of which is to transform all lead compounds retainedby the fibers or fabrics which may still contain acid and be partlysoluble, into non-irritating compounds of lead which are insoluble inwater and the secretions of the human body. For such fixing bathssolutions of various chemicals which are capable of producing insolublelead compounds may be used. Mild alkalis may be used, such ascarbonates, phosphates, or silicates of alkali metals, the phosphateshaving been found in general to be the best.

After the fixing bath the material is usually rinsed again, but this isnot indispensable. Besides producing the required insolubility of thelead compound, the fixing bath restores to the partially-weighted fibersor fabrics the ability to take up additional quantities of lead from thebasic lead solution. After further immersion in the basic lead solution,the additional lead taken up is rendered insoluble by another fixingtreatment, and the complete cycle of operations, i. e., basic leadsolution, rinse and fixing, may be repeated, until the desired amount ofweighting is accomplished. A final bath of silicate of soda may be'used,but this is not essential.

The dyeing of fibers or fabrics weighted by my process may be carriedout in the usual manner.

Fibers and fabrics weighted by my process vary in appearance, especiallyin lustre, according to the degree of basicity used in the leadsolution, higher basicity resulting in general in greater reduction ofthe natural lustre of the fiber. This is particularly true of artificialsilk. I am thus able to control the delustering effect by control of thebasicity of the lead solution.

My product possesses greater tensile strength, elasticity and durabilitythan materials weighted by the usual tin weighting process, or byprocesses requiring substantial previous applications of tin or othermetal salts.

My preferred product is a silk weighted to the desired extent with alead compound only. Neutral or acid solutions of lead are capable innormal operation of weighting silk fibers only to a very minor extent.In U. S. Patent No. 1,845,037 to Clavel, for example, it has beensuggested to pass silk through a phosphate bath and then to pass itwithout previous washing into a solution of a metallic salt such asstannic chloride or lead acetate. Such treatment with neutral leadsolutions, however, in the 'absence of preliminary treatment of thefiber with tin, is capable in normal operation of weighting silk fibersonly up to about 30%. By my process I am able to produce fibers weightedwith lead, in the absence of other metal, to any desired extent up tomore than two hundred per cent of the weight of the fiber.

As stated above, no treatment with tin or other compounds preliminary tothe treatment with basic lead salt solution is necessary in the practiceof my invention. Such tin or other treatment may, however, be given tothe fibers without interfering with the treatmentwith basic leadsolutions in accordance with my invention. I therefore claim a processin which the basicity of the lead solution with which the fiber istreated is utilized as the substantial and material factor for causingthe fiber to take up lead, whether or not the fiber is subjected to aminor or superficial treatment with tin or other compounds which doesnot materially affect the afiinity of the fiber for basic lead salts andleaves such fiber substantially free from weighting metal prior to thebasic lead treatment. I also claim a product which is weightedprincipally by treatment with basic lead compounds, although it maycontain minor amounts of tin.

In the appended claims the term silk, unless specifically limited tonatural or artificial. silk, is intended to include both natural silkand/or artificial silk, and the term fiber" includes both the fiber andthe fabric manufactured therefrom.

What I claim is:

1. A process of weighting silk fiber with lead which comprises treatinga fiber which is free from other weighting metals with a solutioncontaining a basic substance and a lead compound, said solution having abasic reaction, and subsequently treating the fiber to fix awater-insoluble lead compound thereon.

2. A process of weighting fiber with lead which comprises treating afiber which is free from other metal with a solution of a lead compound,said solution containing a substance imparting a basic reaction thereto,and subsequently treating the fiber to fix thereon a water-insolublelead compound.

3. A process of weighting silk fiber with lead which comprises treatinga fiber which is free from other metal with an aqueous solutioncontaining a weak alkali and a water-soluble lead compound, saidsolution having a basic reaction, whereby a soluble basic lead compoundis deposited upon the fiber, and then treating the fiber to convert thesaid soluble basic lead compound into a water-insoluble lead compound.

4. A process of weighting silk fiber with lead which comprises treatinga silk fiber which is free from other weighting metals with a solutionof a water-soluble lead compound, said solution having a pH ofapproximately 8, whereby a water-soluble basic lead compound isdeposited upon the fiber, and then treating the fiber to convert thesaid water-soluble lead compound into a water-insoluble lead compound.

5. A process of weighting silk fiber with lead which comprises treatinga silk fiber which is free from other weighting metals with a solutionof a water-soluble lead compound, said solution containing a weak alkaliand having a basic reaction, whereby a water-soluble basic lead compoundis absorbed by the fiber, and washing the fiber with water to convertthe said water-soluble lead compound into a water-insoluble leadcompound, and converting the said insoluble compound at least in part tolead phosphate.

6. A process of weighting silk fiber with lead which comprises preparingan aqueous solution of lead acetate and adding thereto a substanceimparting a basic reaction, thereby providing a basic solution of leadacetate, and immersing silk fiber which is free from tin in theresulting solution, whereby a water-soluble basic lead acetate adheresto the silk fiber, then washing the fiber with water and therebyprecipitating a waterins'oluble basic lead acetate on the fiber.

7. A process of weighting silk fiber with lead which comprises immersinga fiber which is free from other metal in an aqueous solution containinglead acetate and ammonium hydroxide, said solution having a basicreaction, removing the silk and treating the same with a phosphatesolution to precipitate on the fiber a water-insoluble phosphate.

8. A processor weighting silk fiber with lead which comprises immersinga fiber which is free from other weighting metal in an aqueous solutioncontaining lead acetate and lead oxide, said solution having the basicreaction, removing the silk and treating the same with an alkalinesolution to precipitate on the fiber a water-insoluble lead compound.

9. A textile fiber weighted with lead and tree from other weightingmetal, said lead being deposited on the fiber by immersion of the fiberin a basic solution of a lead compound and being fixed thereon bysubsequent treatment to convert the lead absorbed by the fiber into awater-insolubie lead compound.

10. A process of weighting fiber with lead which comprises preparing asolution of a lead compound and adding to the said solution abasicity-imparting substance, thereby providing in solution lead ionsand sufilcient hydroxyl ions to impart a basic reaction to the solution,immersing in the solution a fiber the natural afiinity mersing silkfiber which is free from other weighting metal in the resultingsolution, whereby a water-soluble basic lead compound is absorbed by thesilk fiber, and then treating the, fiber to fix a water-insoluble leadcompound thereon.

BRUNO E. ROE'I'HELI.

